At 298 K, the standard electrode potentials of Cu²⁺/Cu, Zn²⁺ /Zn, Fe²⁺ /Fe and Ag⁺ /Ag are 0.34 V, -0.76 V, -0.44 V and 0.80 V, respectively.

On the basis of standard electrode potential, predict which of the following reaction can not occur?

Concept: 

Relation of reduction potential with reactivity - 

• Reduction potential is the term used in electrochemistry. It is the ability of an element to gain electrons.
• The more negative the reduction potential of an element, the more it will have the tendency to gain electrons. Hence, more easily it will replace the metal atom in salt.
• So, the more the negative reduction potential, the more reactive is the element.

Explanation:

Given reduction potential,  

• Cu²⁺/Cu = 0.34 V 
• Zn²⁺ /Zn = - 0.76 V 
• Fe²⁺ /Fe = - 0.44 V
• Ag⁺ /Ag = 0.80 V

As we know, the more negative reduction potential, the more reactive is the element.

So, accordingly, reactivity order is - Zn > Fe > Cu > Ag.

In displacement reactions, more reactive metal will replace the less reactive metal in salt. For example, Zn can replace the metal in the salt of all three Fe, Cu, and Ag metals, but the reverse is not possible.

Based upon the above statement, as Ag has the lowest reactivity it can not replace any of the given metals in their salts. So, the reaction - 

2 CuSO₄(aq) + 2 Ag(s) → 2 Cu(s) + Ag₂SO₄(aq) is not possible.

Hence, the correct answer is option 1.